try enable CI caches

[baggepinnen]

No description provided.

[JuliaControlBot]

This is an automated message.
Plots were compared to references. 11/11 images have changed, see differences below.
After pulling this PR, please update the reference images by creating a PR to ControlExamplePlots.jl here.

Difference	Reference Image	New Image
❌ 0.047
✔️ 0.011
✔️ 0.001
✔️ 0.001
✔️ 0.007
✔️ 0.003
✔️ 0.0
⚠️ 0.028
❌ 0.06
✔️ 0.0
⚠️ 0.017

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (160423e) 32.99% compared to head (49c8163) 93.16%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #914       +/-   ##
===========================================
+ Coverage   32.99%   93.16%   +60.17%     
===========================================
  Files          43       43               
  Lines        4801     4816       +15     
===========================================
+ Hits         1584     4487     +2903     
+ Misses       3217      329     -2888     

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[baggepinnen]

7->3 minutes for ControlSystems and 17->13 min for ControlSystemsBase